This standard puts obligations on organizations that use email as part of their business operations to protect their users from spam and phishing emails.
DMARC was originally developed to combat email spoofing and phishing. It provides a framework for email authentication.
The standard requires any organization that sends emails to verify their identity using Domain Keys Identified Mail (DKIM). This is done by introducing a _dmarc txt record in your domain's DNS.
The decision between the quarantine option and the email sending system comes down to security vs. convenience.
The none action is used to test DMARC and quarantine messages.
Whether to implement DMARC depends on your company's risk tolerance and goals. We recommend implementing quarantine instead of None to increase the number of spoofed/phishing email messages that get blocked.